1. Field of the Invention
This invention relates to carburetors for internal combustion engines. More particularly, the invention relates to improvements to flow-type carburetors.
2. Description of the Prior Art
A flow-type carburetor automatically atomizes, vaporizes and mixes gasoline and air in the proper proportions necessary for the various power demands of an internal combustion engine. The suction stroke of pistons draws air into the carburetor and through a venturi. The lower pressure created by the venturi draws fuel from a fuel jet or nozzle atomizing, vaporizing and mixing the fuel with the air. The air-fuel mixture then passes through a throttle valve to the engine cylinders.
The amount of fuel mixed with air depends upon the drop of pressure created in the venturi and the volume and velocity of air passing through the carburetor. The openings of the throttle and choke valves and the piston-cylinder suction control the volume and velocity of air and, therefore, control the air to fuel ratio in the air-fuel mixture. Accordingly, the engine power demands and throttle position vary the air-fuel mixture. In most engines the carburetor varies the ratio of air to fuel in the air-fuel mixture from 17:1 to 12:1 depending on the engine operating conditions.
Many carburetors are designed with one or more booster venturis to increase the pressure drop. Various other modifications are known which provide for the increase of fuel in the air-fuel mixture for particular engine operating conditions such as a cold engine, idle, low speed, start, and acceleration. Most of these modifications inject additional fuel into the mixture at or after the throttle valve.
Depending upon the number of cylinders in the engine and the performance desired, engines may be equipped with single, two, three or four barrel carburetors. Multiple barrel carburetors are essentially groupings of single barrel carburetors with the output of each barrel being separately conducted to different cylinders.
It has long been known that the vaporization of fuel in the air-fuel mixture is enhanced by heating. Heat has been provided to the air-fuel mixture by adding exhaust gas to the mixture between the carburetor and the intake manifold for the engine cylinders. Examples of such systems are disclosed in Hallett, U.S. Pat. No. 1,432,751; Kutscher, U.S. Pat. No. 1,099,504; Lovejoy, U.S. Pat. No. 1,201,977; Godfrey, U.S. Pat. No. 2,633,837 and Stille, U.S. Pat. No. 2,419,298.
More recently, efforts have been made to reduce exhaust gas pollution by recirculation of exhaust gas through the cylinders to burn uncombusted or partially combusted fuel entrained in the exhaust gas. This has been accomplished, as in Schultz, U.S. Pat. No. 3,872,845, for example, by injecting manually metered exhaust gas into the air-fuel mixture between the carburetor and the intake manifold during certain engine operating conditions. Bohls et al., U.S. Pat. No. 3,786,793, discloses an additional vacuum actuated valve system for the controlled introduction of additional air and exhaust gas into the air-fuel mixture between the carburetor and intake manifold during certain engine operating conditions. While the exhaust gas recirculation systems reduce pollution, they also have been shown to reduce fuel economy and engine efficiency.
The instant invention improves the performance and efficiency of internal combustion engines and reduces pollution by introducing exhaust gas into a lean air-fuel mixture in the carburetor in the area between the venturi and the throttle valve. The invention is a simple means of reducing pollution while greatly enhancing the efficiency of the engine. No complicated and expensive metering equipment is necessary; the introduction of the exhaust gas into the carburetor above the throttle valve into a air-fuel mixture provides improved atomization of fuel and is automatically metered to be commensurate with engine operating conditions by the carburetor throttle valve.
Road tests of vehicles having standard carburetors modified to incorporate the invention have demonstrated the advantages of the invention. In tests conducted on 1954 and 1962 Ford 5-ton trucks, a 1956 Thunderbird, 1967 Acadian Beaumont, 1958 Ford Custom, 1977 Mazda station wagon, and 1969 Dodge Dart, the invention provided, in most cases, a greater than 40% improvement in fuel economy, a significant reduction in exhaust gas pollution, an increase in engine power, longer life for spark plugs and oil due to less carbon contamination, a lower operating temperature, and continued efficient performance on lower octane fuel. These tests were conducted at various altitudes and over various periods of time.
The invention additionally provides a method for modifying existing engines to obtain the advantages.